The present invention relates generally to inspection systems for packaged heart valves and more particularly to an automated visual inspection system that verifies the presence, correct assembly and orientation of heart valves that have been packaged.
The valves of the heart allow fluid to flow in only one direction through the heart as the chambers of the heart contract in sequence to pump blood through the body. Hence, proper operation of the valves is essential to life. For various reasons, one or more of the valves may become defective or diseased, with the result that it no longer performs adequately. It is currently common practice to replace such defective or diseased valves with mechanical or prosthetic valves that provide the same function.
Referring initially to FIG. 1, mechanical prosthetic heart valves typically include a rigid ring or annulus 11 supporting one, two or three rigid leaflets 13. The leaflets are mounted in the annulus so that they can pivot between open and shut positions and thereby control the flow of blood through the valve. In FIG. 1 a bi-leaflet valve is shown with the leaflets in the open position. The rigid annulus 11 and leaflets 13 are commonly formed of pyrolytic carbon, which is a particularly hard and wear-resistant form of carbon. Because pyrolytic carbon is relatively brittle, however, the annulus itself is often surrounded by with a stiffening ring 15, which may be made of titanium or cobalt chromium. In a typical configuration, the annulus and stiffening ring are both captured within a knit fabric sewing cuff or suture cuff 17, as shown in FIG. 1. After the defective or diseased natural valve has been removed, the prosthetic valve is placed into the valve opening and the sewing cuff is sutured to the patient""s tissue. Over time, tissue grows into the fabric of the cuff, providing a secure seal for the prosthetic valve. With each contraction of the heart, the leaflets swing open to allow blood to flow, and then closed to prevent backflow, thereby allowing blood to flow in one direction only.
Because the prosthetic valve must fit snugly into the tissue annulus and yet provide the largest possible fluid flow opening, prosthetic valves come in a range of sizes. The incremental increase in diameter from one valve size to the next is typically 2 millimeters and most commercial valve makers provide 5 to 8 valve sizes.
In addition, prosthetic valves are manufactured in a variety of shapes and configurations. For example, aortic valves are configured differently from mitral valves (leaflets open upward instead of downward), a variety of sewing cuff shapes are provided to allow an optimal fit with the heart and tissue annulus, and the valves themselves are provided in a variety of configurations in order to accommodate the various preferences of physicians. FIG. 2 shows an exemplary but not exhaustive variety of assembled heart valves. The variations in prosthesis shape and type, when multiplied by the number of sizes in which those variations are required, results in a large total number of prosthetic profiles. This complexity can affect inspection processes, as discussed below.
While several of the components of a prosthetic heart valve are machine manufactured, final assembly of each valve is typically done by hand. This is because assembly of the cuff onto the annular valve ring requires intricate stitching that is not readily accomplished by a machine. In addition, the valve components must be handled carefully, as they may be permanently but invisibly damaged by the application of excessive stress. Once a prosthetic valve is completely assembled, it is placed in a first package, which supports the valve in a particular desired orientation. The first package is then sealed in a second package, which protects the prosthetic valve from contamination during shipping and storage. The prosthetic valve is sterilized after being sealed in the second package. As part of rigorous quality control procedures, each valve is typically assigned a serial number.
The heart valve manufacturing process typically includes multiple quality control steps, one of which includes a visual inspection of the prosthetic valve as it will be placed in the first package. One purpose of this step is to ensure that the prosthetic valve in question is actually the valve size and type that is supposed to be associated with the assigned serial number. Another purpose is to ensure that the prosthetic valve is properly loaded into the first package. Still another purpose of this inspection step is to ensure that the components of the valve under test are properly assembled and have not become dislodged or broken.
One common method for carrying out the visual inspection system is to allow a human operator to view each valve package and compare it to an image of the valve under test. This method requires that the operator maintain a complete focus on the inspection process and that the inspector accurately compare each unit to the information available on that unit. Hence, it is desirable to provide a system that eliminates human involvement from the inspection process.
The present invention provides an inspection system that is capable of comparing each packaged valve unit to the data record for that unit to ensure that the valve is the size and type that it is supposed to be. The present system uses a visual imaging system that includes a point by point comparison of portions of the actual valve image with expected values that are stored in a database. Hence, the present system is able to inspect and track a virtually unlimited number of different valve types, sizes and configurations and provide a reliable pass/fail output for each unit.